Mimas

Mimas is a moon of Saturn which was discovered in 1789 by William Herschel. It is named after Mimas, a son of Gaia in Greek mythology, and is also designated Saturn I.

With a diameter of 396 kilometres (246 mi) it is the 21st-largest moon in the Solar System and is the smallest astronomical body that is known to be rounded in shape because of self-gravitation.